There's a lot of theories on who exactly Morgan is or where he/she came from. His/Her's complexity and mystery are one of the reasons why they're one of my favorite characters in the game. Personally, I believe that they came from the Future Past DLC, so spoilers there. As for their "amnesia"...yeah I don't think so. Anyways, this is my take on it, so I hope you enjoy. Thank you!
Morgan was a liar.
Everything that he pretended to be and said was all a lie.
He fooled everyone. But was it really his fault? Could you blame him for lying about himself? About his past, about his amnesia…
The gods were kind and merciful to him, for he did not deserve this second chance. He deserved to die. To be forgotten, to be left behind. The acts he had committed where unforgivable, yet he was deemed worthy of a second chance.
He knew what he did and for whom he did it for. He was the cause of the many deaths in the future. All the destruction and chaos were all orders from her. And he would do it again if he had to…
When he awoke in the strange ruins, he was utterly lost. He did not recognize this place. And while he tried to get his bearing, he heard footsteps from down below confirming he was not alone. He gripped his tome and sword tightly till his knuckles turned white. If they were Naga's children then he had no other choice but to fight. And fight to the death he would. He wouldn't dare let them reach Master Grima.
A few moments later and a group of people did indeed appear near the entrance of the ruins. But they were not the usual group of children he knew. Instead, it was a band of older looking soldiers. They did not look that much older, but they had a look in their eyes that made them seem as though they knew what they were doing. A certain tinkle of wisdom you could say.
But Morgan did not care who they were. They were not Grimleal and they weren't Master Grima, so they needed to be cut down. He knew a straight approach would be suicide. Moth- Master Grima taught him better. At times like these he would usually summon the Risen at his side, but the undead soldiers refused to listen or give him the time of day. What was going on here? Why did he feel weak…disconnected? This strange place, these people, the Risen…Even the Mark on the back of hand looked faint.
In the midst of his confusion, he did not notice as the band of soldiers began inching ever closer to his direction. It was only the light tapping on his right soldier did he snap out of his delusional state. He snapped back and raised his sword in front of him as a means of defense. In that moment he expected the stranger to attack him or perhaps tackle him to the ground, but the stranger did neither. Instead he had a curious expression on his face, an almost friendly looking one. "Who are you? Why are you here? This is hardly a safe place to be wondering alone."
Morgan stared him down, indecisive on what to do. If he killed the man now, the rest of others would surely be alerted. Perhaps he should play dumb for now.
"M-my name is Morgan…I think. I don't remember much really…I think I may have bumped my head or something," Morgan said pouting. He held his head in his hands and pretended to be under a bit of pain. Let's see how much of a fool this man really is.
The man stepped forward and touched him lightly on his arm, completely letting his guard down. "You alright? My name is Chrom. And finding amnesiacs is apparently my special talent. You remind of a very close friend of mine named Robin. In fact, you do resemble her somewhat…"
Morgan flinched when he heard the name Robin. Morgan knew very little of Master Grima's past, but he did know that in her past life she carried the name Robin. Could it be?
Letting his curiosity take the best of him, he questioned, "Is this Robin by any chance a tactician?"
"She is." Chrom answered. "Do you know her? Are you related to her at all?"
"Th-That's Mother!" Morgan shouted. He had not said the word Mother in a long time, it felt oddly strange on his tongue. He knew it was probably the wrong idea to divulge who he was, but knowing that she could be nearby…
"So if you're her son, then I take it you came here from the future. Do you know of somebody named Lucina?"
"F-Future?! Sir, how is that possible? And I don't know of any Lucina." Morgan lied. He knew that name all too well. She was the exalted princess of Ylisse, and the supposed leader of the band of children. She was easily recognizable by the rest of the bunch with her blue hair and her sword, Falchion. For many years Master Grima pined after the sword, but she was never successful. The Mark of Naga in her left eye made it clear the two were destined to enemies.
"Calm down. We can sort this out later with Robin. For now, just follow me, alright?"
Morgan nodded slowly. "Th-thank you, sir. I can defend myself, you don't have to worry."
Chrom nodded and turned around to face the other way, revealing the Exalted symbol on his arm. Morgan's breath hitched and he was ready to bolt out of there. He was in real trouble now. If they saw he carried the Mark of Grima…they would surely kill him on the spot. Morgan gulped and held his weapons even tighter. If he had to fight, then he would be sure to bring others down with him.
Or so he thought he would.
When the fighting was over, Chrom escorted him over to "Robin". She stood there, looking around the camp, directing the others to the medical tents and shouting out orders for others. He had not seen her like this in so long. Her skin was milky white, not ashen or rough as he had come to known. Her hair was long and white, the color of fresh snow. And her eyes were a warm chocolate brown, not the menacing red that pierced through the darkness of the night. It was almost too good to be true.
When he approached her, he had nothing to say. It was Chrom who introduced him to her. When Chrom said that he was his son, her eyes widened and she stepped back. Her eyes scanned him over and over again, her expression of amazement and shock would not leave. She reached out to touch him on his forehead. She brushed his forehead with her thumb ever so gently and her expression softened. She grabbed a strand of his orange hair and smiled at it. "Just like your father," she murmured.
Hearing her soothing voice, Morgan could not take it any longer. He jumped into her arms and cried out to her. He held her tightly, relishing in her soft form and sweet scent. If he had tried to do this back in the future, Master Grima would have killed him right then and there. And even if this was still Master Grima in disguise, he did not care. All he wanted to do was hold his mother, for once in his life.
When she asked about his past and origins, Morgan lied on the spot. He claimed to have "lost his memory", laughing it off as a joke. When he expected her to accuse him of lying, she believed him. All he remembered was his mother and her tactics, and that was that, which wasn't such a lie. All his life was devoted to his mother, he never met his father. The only remains Master Grima gave him was a worn down bandana.
While it was only a small sentiment, he kept it for years. Whenever he was sent out to missions or scavenges, he would secretly look for sewing materials to keep repairing the fabric. Battle after battle, the thing was torn and dirtied to absolute hell. But it was one of the only things he held dear.
When he actually met his father, he did not expect…whatever he was. His father was a thief of sorts with quite an obsession of candy. One of the first questions he asked Morgan was if he had a sweet tooth. Morgan, going along with it, nodded and said that he couldn't keep his hands off of the sugary stuff. His father smirked and ruffled his hair. He immediately whipped out a lollipop from gods knows where and shoved it into Morgan's hand and he left without saying good-bye.
Morgan looked at the sweet with confusion. Food was scarce in the future and he was sure he never had candy before. He tentatively opened the wrapper and stuck the candy in his mouth. The overbearing flavor of sweetness and sour made his lips pucker up and face scrunch up. He pulled the lollipop out of his mouth and coughed. The sweet flavor left him with a bad taste in his mouth and he swore he tasted bile in the back of his throat. Nevertheless, Morgan stuck through it and ate the candy throughout the day until he finished. When he was finally done he promised never to have the treat again…That is until a couple of minutes later when his father dropped a chocolate bar in desk. No wonder Master Grima killed him off.
As their journey continued, more and more of the children were found. And much like Lucina, they all remembered their parents quite well. He half expected them to attack Morgan as soon as they recognized him, but he only got strange looks instead. He tried to distance himself from them as much as possible, refusing to meet their eye. But boy were they persistent.
Whenever they approached him, Morgan turned into the, oh so optimistic Morgan everyone had come to know and love, a fake facade of happiness and absolute innocence. Really, he played quite the actor.
And even though he wanted nothing to do with them, he found himself growing fond of his newly found friends. Whether it was his rivalry with Owain, or training with Kjelle, he could not stop himself from feeling as though he fit in with them. His emotions for them grew so strong he even ended up marrying Noire, the child of dark mage that loved the "darkness" that was his mother.
It was strange when he heard the children talking of the future. How the talked on how terrible it was, how terrifying and hopeless world it was. They said they were jealous of Morgan's amnesia, that they wished they could forget everything. Little did they know that it was him and his mother's fault for all of this. That there were moments Morgan was so close to killing one of them whenever they crossed paths. If anyone one of them had bad memories, it was certainly him.
Even in the middle of this war, Morgan found himself loving life. The world breathed color and life into him, a site he thought he would never see. Simple conversations and activities excited him to no end. Cooking, cleaning, reading, hugging, sleeping, such menial tasks were joys for him. Having his mother so close to him and speaking to her in a loving matter was surreal to him. Eventually after time he even began to enjoy his father's candy, even when it caused the back of his throat to burn and his teeth to ache.
He was lucky, so damn lucky. He didn't know what he did to deserve this, but he knew a million reasons of why he didn't. He was the son of Grima, yet Naga still showed mercy to someone like him. Every night he gave a silent thank you and prayer to the dragon. He only wished he knew what happened to his sister. Back in the future, the two did not interact much, Grima forbade it, but Morgan knew fully well who she was. Whether she ever made it out, or she stayed behind and perished, he did not know. He never mentioned her to any of the others nor his parents. He was too selfish. He had them all to himself…and he didn't want that taken away.
When it was finally revealed to the Shepherds that Robin was Grima, everyone grew afraid. The evil dragon which sought to destroy the world was actually their beloved tactician. When Robin refused to take her role, the other Robin from the future, his mother, took on the role for her. When Morgan saw her again at the Table where she resided most of the time, she gave him a wicked smile that sent him shivers. "So that's the game you play."
But from there on, she no longer acknowledged him. Now he was an enemy, a useless pawn that no longer held any meaning. Now his place was at the Shepherds side, with the children of Naga.
And when the time came to fight Grima, he held no regrets. His beloved mother was not this monster. All those years of pain and suffering with no rewards or any goals. His mother was not a monster. His mother was not a dragon that storied castles. His mother was not the Fell Dragon! His mother was the famous tactician of Ylisse. The kind mother who gave him purpose in life once more. And he refused to let this beast ruin the beauty of this world. He owed many people many things…and he wouldn't allow them to go to waste.
Mother... You can't leave me now. Not like this...